I just noticed that the schematic is available on this forum at this post - https://www.freestompboxes.org/viewtopic ... ck+deville.
There's a mosfet connected at the output of the pedal with a large resistor that pulls the gate to 0v normally, but a few ms before the relay switches the microcontroller probably pulls the gate high so the signal muted and no pop is heard.
My question is - how can this be a mosfet? it has a body diode and with voltages above it's forward voltage the signal will be clipped, so how come this works? Are we sure this is a mosfet and not a BJT? I have used Jack's clickless system and he uses a 2n5088 BJT and not a mosfet.
Regarding the Jack Deville Deuce Coupe Bypass System
Both MOSFETs and BJTs have some significant limits here. Neither one can mute big signals both well and quietly.
The MOSFET is limited to signals of a diode drop peak before it distorts, as you have guessed. A BJT can do bigger signals, but has offset voltage and other issues. A P-channel JFET is probably better on most counts except availability and price.
If you want to do it well, use an LED/PhotoFET like the H11F1/2/3 or an LED/LDR, which is expensive *and* slow.
The bang-up job is probably two MOSFETs connected in series source to source, with suitable isolated gate drive like an LED to photovoltaic. That gets pretty good, but is expensive for parts and PCB real estate.
There are special cases where you can use a switch not to totally mute, but to simply lower the impedance the relay-crosstalk-clik works into. This helps a lot. But you have to know what you're doing and what relay you're going to be using.
The MOSFET is limited to signals of a diode drop peak before it distorts, as you have guessed. A BJT can do bigger signals, but has offset voltage and other issues. A P-channel JFET is probably better on most counts except availability and price.
If you want to do it well, use an LED/PhotoFET like the H11F1/2/3 or an LED/LDR, which is expensive *and* slow.
The bang-up job is probably two MOSFETs connected in series source to source, with suitable isolated gate drive like an LED to photovoltaic. That gets pretty good, but is expensive for parts and PCB real estate.
There are special cases where you can use a switch not to totally mute, but to simply lower the impedance the relay-crosstalk-clik works into. This helps a lot. But you have to know what you're doing and what relay you're going to be using.
Thanks for the reply RG. I also imagined that a P channel JFET would pop up (no pun) in this discussion. I see what you say, however is there any way to address the actual usage of a BJT and MOSFET in the said circuits by mr. Deville? Just to make it clear, I am just wondering how his circuit works and what id does. Not looking to go any further than that.
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Jack Deville
- Resistor Ronker
Information
Are you smokin base?tss332 wrote:I just noticed that the schematic is available on this forum at this post - https://www.freestompboxes.org/viewtopic ... ck+deville.
There's a mosfet connected at the output of the pedal with a large resistor that pulls the gate to 0v normally, but a few ms before the relay switches the microcontroller probably pulls the gate high so the signal muted and no pop is heard.
My question is - how can this be a mosfet? it has a body diode and with voltages above it's forward voltage the signal will be clipped, so how come this works? Are we sure this is a mosfet and not a BJT? I have used Jack's clickless system and he uses a 2n5088 BJT and not a mosfet.
To be serious, I'd recommend rechecking your BOM.
Just sayin. I designed it.
Hello Jack, I'll do that (check the parts, not smoke anything...). The mosfet came from the schematic posted here and I have one of your clickless systems on the way from Mammoth. I just wanted to have an idea of how it's done because I want my guitar signal to remain as intact as possible and both mosfet and a bjt are somewhat non trivial for muting.
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electrosonic
- Breadboard Brother
I think the cool thing is that the transistor (p-channel jfet?) turns on faster than the relay, so it mutes the audio before the relay moves. Some other setups I have seen use a another output for the mute - which adds a little complexity in the programming. Setting up the timing to mute then move the relay and then unmute. Not a big deal I guess because you only have to write the program once.
Andrew.
Andrew.